The present invention relates to enhancing the range in a wireless communication application where communication devices may transmit multicast signals as well as directed signals.
Composite Beamforming (CBF) is an antenna processing technique in which a first communication device, having a plurality of antennas, weights a signal to be transmitted by its antennas to a second communication device also having a plurality of antennas. Similarly, the second communication device weights and combines the received signals received by its antennas. The transmit weights and receive weights are determined to optimize the link margin between the devices, thereby significantly extending the range of communication between the two communication devices. Techniques related to composite beamforming are the subject matter of commonly assigned co-pending applications filed on even date and entitled “System and Method for Antenna Diversity Using Joint Maximal Ratio Combining” and “System and Method for Antenna Diversity Using Equal Gain Joint Maximal Ratio Combining,” the entirety of both which are incorporated herein by reference. There are other techniques to improve the link margin for directed signal transmissions between two communication devices, including antenna selection diversity, for example.
Link margin improvement translates into a corresponding improvement in range, data rate at a given range, infrastructure cost to support a given data rate, and interference immunity. However, the range improvement afforded by CBF applies to signals that are sent in a point-to-point fashion from one device to another. Many wireless applications also require multicast signal communication, i.e., point to multi-point. Therefore, to improve the overall range related parameters of a wireless application, it is necessary to also improve the range of multicast signal transmissions. No such range improvement techniques for multicast communication are heretofore known.